Flux used in the making of steel



United States Patent C 3,320,052 FLUX USED IN THE MAKING OF STEEL JamesJ. Bowd'en, P.0. Box 127, Cortland, Ohio 44410 No Drawing. Filed Sept.17, 1964, Ser. No. 397,302 2 Claims. (Cl. 75-53) My invention relates toa flux used in the making of steel, and to the method of producing suchflux, and the principal object of my invention is to produce new andimproved flux and methods of making the same.

In US. Patent No. 2,283,622, issued to James 1. Bowden and John S. Suda,there is disclosed an improvement in the manufacture of iron and steelthrough the incorporation of alumina (A1 in such proportion as to securein the tapping or draw off slag the presence of a suflicient amount ofalumina to replace or inhibit an excess of iron oxide (Fe O whichotherwise would be present in such a slag in the form of calciumferrites.

The present invention provides a further improvement in that thenecessary alumina is provided at a greatly reduced cost, withoutsacrificing any of the beneficial results obtained through use of theprocess disclosed in said patent. As a matter of fact, the alumina isderived from sources which heretofore represented waste products andwhich required treatment to reduce the obnoxiousness thereof.

More specifically, I have discovered that the exceedingly fine powderwhich resulted in the aluminum smelting process and which heretofore wasnot only considered a waste but also presented problems in reducing itto proper waste form, may be effectively used to provide the alumina andcryolite used in the patented process aforesaid. Alumina is very usefulin a slag making process, as is cryolite. The fact that cryolite has notheretofore been extensively used is because it is expensive to produce.However, its presence in a waste product provides an extra which is verybeneficial.

As background explanation, in the aluminum smelting process aluminum isseparated from the oxygen with which it is combined in nature by passingan electric current through a solution of cryolite, in which solutionthe alumina is dissolved. T o accomplish this reduction, a directcurrent is passed through large, carbon-lined smelting pots which arefilled with molten cryolite (sodium aluminum fluoride) in which alumina(A1 0 is dissolved. The principal materials for this electrolyte are afinely crushed cryolite containing approximately 6% calcium fluoride and9% aluminum oxide. It has been found that the fluorspar may vary from 1%to 10% and the aluminum oxide may vary from 2% to 9%.

The passage of electricity through the solution causes metallic aluminumto be deposited on the bottom of the pot (cathode) while the oxygen thatwas part of the alumina combines with the carbon anode and is releasedas carbon dioxide gas (CO This smelting process is continuous andperiodically molten aluminum is siphoned from the pot (or cell as it istechnically named). As the alumina content in the cryolite bath isreduced, more alumina is added from time to time to the pot. Heat whichis generated by the passage of the electric current through the mixturein the pot maintains the cryolite bath in a molten condition so that itwill continue to dissolve the added alumina and cryolite.

In the foregoing procedure, the addition of alumina, cryolite andfiuorspar'which are in the form of exceedingly fine powders, creates atendency to produce a diff-used, dusty atmosphere containing alumina,fluorspar and cryolite. The dust is detrimental to efiicient operationsand thus an elaborate dust collecting system had to be provided toeffectively remove the unwanted dust. In order to prevent the dust fromagain being airborne after it is removed from the smelting area, thedust is taken through a series of water sprays and ultimately collectedas a slurry and taken through pipes to a refuse area which may be anexcavated hole or some other storage means as tanks and the like.

The sludge is fifty or more percent water when it comes from the dustcollecting system and the following arrangements present typicalanalyses of the solids present in sludges which contained about 53.1%water:

Arrangement No. l Solids: Percent Fluorine (F) 22.0 Sodium oxide (Na O)15.7 Silica (SiO 5.9 Ferric oxide R1 0 2.4 Alumina (A1 0 19.1 Carbon 5.1Calcium 28.3

Total 98.5

Arrangement No. 2 Solids: Percent Cryolite (Na AlF 28.8 Fluorspar (CaF12.7 Lime (CaO) 30.5 Alumina (A1 0 12.1 Silica (SiO 5.9 Carbon 5.1Ferric oxide (Fe O 2.4

Total 97.5

The small percentage difference between the above and is represented bymaterials which are of no great importance to the present matter. Itwill be understood that the above arrangements are typical and that manyvariations in the specific analysis of other sludges may exist.

I have discovered that the composition of the sludge resulting from analuminum smelting system may be used to good advantage in treating slagin a steel making process, such as disclosed in the above-mentionedpatent. In a patent issued to me and John S. Suda, No. 2,480,901, thereis disclosed the use of aluminum dross resulting from an aluminumsmelting process, but at that time it was considered necessary to drythe slurry and this represented considerable storage time to dry itnaturally, or considerable expense in equipment to dry it morehurriedly. In a subsequent patent (No. 2,927,852), issued to me, Iproposed the intimate mixture of powdered aluminum dross with liquifiedcoal tar or pitch, so that briquettes may be formed.

I have now discovered that the sludge which results as a waste productin an aluminum reduction or production system may be directly used inthe treatment of steel making slag although because of the difiiculty inhandling it and the danger of introducing it moist to the hot charge ofthe steel furnace, I found it preferable to mix the sludge with lime,limestone, iron oxide, mill scale, dolomite, or aluminum dross or acombination of the same, to more nearly approach the composition of afinished steel making slag. An addition-a1 advantage in adding theforegoing minerals is found in the fact that they absorb the moisture ofthe sludge and therefore make for a more easily workable and usuablecomposition, and also eliminate the danger of introducing a moistcomposition to the highly heated steel bath.

The approximate composition (theoretical) of the minerals that may beadded to the sludge are given below:

Flux mixed with sludge CaO MgO S102 Al O CO Limestone 54.0 88 61 28 43.50 Burnt Lime 95.0 .75 .95 1. 41 1. 65 Raw Dolomite--. 30. 30 21. 56 l448 47. 28 Single Burnt Dolomite... 44. 8O 34. 48 56 1.12 18. 30

The above-noted flux, which are standard steel making flux additions,become part of the chemical makeup of the steel making slag, and thefusion of this flux to produce a steel making slag is aided by thecomponents in the sludge, such as the minerals cryolite, fluorspar,lime, alumina and ferric oxide, as designed in arrangement No. 2 above.

A typical analysis of a steel making slag is given below, together withthe composition of the accompanying heat of steel that underlies suchslag:

For the same heat of steel The constituents contained in the sludgewhich results as a waste in the aluminum smelting industry include suchminerals as cryolite, fluorspar, alumina and iron oxide, all of whichare in themselves very useful in fluxing the lime in the steel slagmaking process, so that the sludge itself, when dried, may be used as anexcellent flux to, and as an aid in the solubilitizing of the lime, inthe slag making charge.

In addition, however, this sludge is much more versatile in that it maybe mixed with various proportions of one or more of the ingredientsincluding limestone, lime, iron oxide or mill scale and raw or burntdolomite to make a less potent but nonetheless highly useful fluxaddition to the steel making charge since in so mixing these very basicmaterials with the sludge none of the basic values which are sonecessary in the steel making process are lost.

As much as six parts of limestone or lime (CaO) may be mixed with onepart of this aluminum sludge to produce a mixture that may besubstituted for the standard lime charge used in all of the varioussteel making practices, such as open hearth, electric and oxygenprocesses. Further, since the sludge carries with it fifty percent ormore of water, it may be successfully dried by mixing one to ten partsof lime, limestone or dolomite with the sludge, after which it isthoroughly mixed by mechanical means.

In some cases where it is required that the resulting mixture be in someform that will facilitate handling, the mixture may be briquetted and incases where briquetting is desirable and a more durable briquet isrequired, a small amount (3% to 10%) of cement, either the Portland, oraluminate, variety, may be added to the mixture, and the latter thenpermitted to set up. In other cases, the mixture may be put through abriquetting machine, such as a Komarek Greaves briquette machine, toform briquets which are easily handled.

Composition of specimen mixtures of the sludge with other flux such aslimestone, lime and dolomite are shown below. The designated specimenmixtures use limestone as an example and illustrate theoreticalvariations result ing from such mixtures.

SPECIMEN MIXTURES OF SLUD GE AND OTHER FLUX Material Parts CeO MgO S107A1103 F8203 CaFg Cryolite CO1 Carbon Total Sludge 100 30. 5. 90 12. 102. 40 12. 70 28. 80 5. 10 97. 50 Limestone. 106 53. 50 80 61 14 14 44.0099. 19

Total r 200 84.00 80 6. 51 12.24 2. 54 12. 70 28. 80 44.00 5. 10 Average100 42. 0O 40 3. 25 6. 12 1. 27 6. 35 14. 40 22. 00 2. 98. 34

sludgem, 100 30. 50 5. 90 12.10 2. 46 12.76 28. 80 5. 10 97. 50Limestone 200 107.00 1. 1. 22 .28 28 88.00 198. 38

Total," 300 137. 50 1. 60 7. 12 12. 38 2. 68 12.70 28.80 88.60 5. 10297.88 Average. 100 45. 83 53 2. 37 4.13 S9 4. 23 9. 60 29. 33 1. 70 96.

SI udge A- 100 30. 50 5. 90 12. 10 2. 40 12.70 28. 80 a. 5.10 97. 50L1n1est0ne 300 160. 50 2. 40 1. 83 42 42 132.00 297. 57

TotaL 400 191. 00 2. 4O 7. 73 12. 52 2.82 12. 28. 80 132. 00 5. 10 395.67 Average 100 47. 60 1. 93 3. 13 .70 3.17 7. 20 33. 00 1. 27 98. 7

Sludge, 100 30. 50 5.90 12. 10 2. 40 12.70 28.80 5. 10 97. 50 Limestone500 267. 50 4.00 3. 66 70 .7 220.00 495. 95

Total 1- 600 298. 00 4. 0O 9. 56 12. 8O 3. 10 12. 70 28. 220. 00 5. 10493. 45 Average 100 49.67 67 1. 59 2.13 .52 2. 12 4. 80 36. 67 .85 99.62

Sludge 100 30. 50 5. 12. 10 2. 40 12. 70 28. 80 5. 10 97. 50 L1n1estone600 321.00 4.80 3. 66 84 .84 0.00 0.00 264. (10 6.00

Tota1 700 351. 50 4.80 9. 56 12. 94 3. 24 12.70 28. 80 264.00 5.10Average 50. 30 69 1. 36 1.85 .46 1.81 4. 12 37.71 .73 98. 96

Sludge 300 90. 90 17. "0 36. 30 7. 20 38 10 86. 40 15. 30 291. 90 RawDolom 100 30. 30 21. 56 l4 24 .24 47. 28 99. 76

Total- 400 121. 20 17.84 36. 54 7. 44 38. 10 86. 40 62. 58 390. 66Average. 30. 30 5 39 4. 46 9.14 1.86 9. 52 21.60 15.64 97. 66

I have also found that red mud, which is a waste product in theproduction of alumina, may be used in place of the sludgeaforementioned.

In an article entitled Basic Principles of Bayer Process Design,contained in vol. I of a book entitled Extrac- 6 slag making flux of aquality as high as, and at a cost much lower, than the slag making fluxhereinbefore used.

In view of the foregoing it will be apparent to those skilled in the artthat I have accomplished at least the 5 principal object of my inventionand it will also be aptive Metallurgy of Aluminum, published byInterscience parent to those skilled in the art that the embodimentsPublishers, a division of John Wiley & Sons, the authors, hereindescribed may be variously changed and modified, A. N. Adamson, E. I.Bloore and A. R. Carr, discuss without departing from the spirit of theinvention, and the chemical considerations affecting the Bayer processthat the invention is capable of uses and has advantages for theproduction of alumina from bauxite found in 10 not herein specificallydescribed; hence it will be apprecivarious forms throughout the world.ated that the herein disclosed embodiments are illustra- Briefly,alumina is extracted from bauxite under contive only, and that myinvention is not limited thereto. ditions chosen to facilitate theremoval of silica. Pri- Iclaim: mary separation may be carried out incontinuous settling 1. The method of producing a low-cost steel-makingand thickening equipment, or in filters depending upon flux from a wasteproduct produced in the manufacture the settling or filtrationcharacteristics of the residue. In of aluminum by melt electrolysis of asolution of alumiany event, the residue, termed red mud, although it isnum oxides in molten fluorides, said oxides and fluorides largelyconsidered a waste material, has a sufiiciently high being introducedinto the melt furnace in genrally powcontent of alumina to make itattractive to be used in dery state wherein a dust is formed by suchintroduction carrying out my invention. and whereby dust particles areentrained in the gas As before, the red mud is preferably mixed withvarious formed in the reduction of aluminum oxides to aluminumproportions of one or more of the ingredients including metal, said dustbeing collected and treated with water to limestone, lime, iron oxide ormill scale, and raw or burnt inhibit its tendency to remain airborne andsaid water dolomite to eifect drying of the red mud and to producetransforming the dust into a sludge, the method coma highly useful fluxaddition to the steel making charge. prising adding to and mixing withthe sludge materials The dried or almost dry mixture may be briquetted,if selected from the group consisting of lime, limestone, desired, andcement may be added to the mixture to iron oxide, mill scale anddolomite until the water in the facilitate drying and briquetting.sludge is absorbed to the extent that the mixture may be The followingcharts provide examples of the mixtures safely charged into asteel-making furnace as a flux to and percentages of ingredients usefulin making a good 0 assist in the steel-making process. steel makingslag: 2. The method of claim 1 and further including the Parts 030 S102A1205 F6203 'liOz N320 Igiution Total Red mud 100 28.72 27.79 15.38 1.07 15.19 10. 79 98.94 Burnt Lime 100 94.74 .96 .49 1.65 94.74

Total 200 94.74 29.68 28.28 15.38 1.07 15.19 12. 44 197. 68 Average 47.37 14.84 .14 7. e9 .53 7.59 9.22 98. 84

Red mud 100 2 72 27.79 15.38 1.07 15.19 10.79 98.94 Burnt Lime 400378.96 3.84 1.96 6.60 394.96

Total"--. 500 378.96 32. 56 29.75 15.38 1.07 15. 19 17.39 493.90 Average75.79 3. 51 5.95 3.07 .21 3.04 3. 48 98.78

If briquetted add from 3% to 10% cement to act as step of adding abinder material to the mixture and then binder. briquetting theresultant.

MIXTURES OF RED MUD AND LIMESTONE Parts 030 S101 A1203 F5 0 T10 N220IgInition Total Red mud 190 28. 72 27. 79 15.38 1. 07 15.19 10. 79 98.94 Limestone 100 15.50 75 50 .50 44. O0 99. 20

Total 200 53. 50 29. 47 28. 29 15.88 1. 07 15. 19 54. 79 198. 14Average. 100 21. 75 14. 73 14. 15 7. 94 53 7. 59 27.39 99. 08

Red mud. 100 28. 72 27.79 15. 38 1. 0 15.19 10. 79 98. 94 Lnnestone 400214. 00 3.00 2. 00 2. 00 176.00 397. 00

Total 500 214. 00 31. 72 29. 79 17. 38 1. 07 15. 19 186. 79 495. 94Average 42. so 6. 34 5. 96 3. 47 .21 3. 04 37. 39 99.19

If briquetted add 3% to 10% cement to act as a References Cited by theExaminer bmder- UNITED STATES PATENTS I have also d1scovered that thedust recovered from the milling of aluminum skimmings may be used a adrying 2,416,179 2/1947 Kemmer agent with either the sludge or red mudaforesaid, and 2,480,901 9/1949 Bowden et a1 such dust may be used aloneor in combination with any 9/1958 Rossborough 75'53 one of the dryingingredients mentioned above. if' 1 3 3 It w'll be a re 'ated that 111dd't' of th b r 4 Pp e a 6 mm 2,947,673 8/1960 Sem et al. 204-247 eralsas above denoted, act as dryers for the sludge and making it moreamenable to its preparation for use as a BENJAMIN HENKIN, PrimaryExaminer.

1. THE METHOD OF PRODUCING A LOW-COST STEEL-MAKING FLUX FROM A WASTEPRODUCT PRODUCED IN THE MANUFACTURE OF ALUMINUM BY MELT ELECTROLYSIS OFA SOLUTION OF ALUMINUM OXIDES IN MOLTEN FLUORIDES, SAID OXIDES ANDFLUORIDES BEING INTRODUCED INTO THE MELT FURNACE IN GENRALLY POWDERYSTATE WHEREIN A DUST IS FORMED BY SUCH INTRODUCTION AND WHEREBY DUSTPARTICLES ARE ENTRAINED IN THE GAS FORMED IN THE REDUCTION OF ALUMINUMOXIDES TO ALUMINUM METAL, SAID DUST BEING COLLECTED AND TREATED WITHWATER TO INHIBIT ITS TENDENCY TO REMAIN AIRBORNE AND SAID WATERTRANSFORMING THE DUST INTO A SLUDGE, THE METHOD COMPRISING ADDING TO ANDMIXING WITH THE SLUDGE MATERIALS SELECTED FROM THE GROUP CONSISTING OFLIME, LIMESTONE, IRON OXIDE, MILL SCALE AND DOLOMITE UNTIL THE WATER INTHE SLUDGE IS ABSORBED TO THE EXTENT THAT THE MIXTURE MAY BE SAFELYCHARGED INTO A STEEL-MAKING FURNACE AS A FLUX TO ASSIST IN THESTEEL-MAKING PROCESS.